Plasticizers found in various common plastic intravenous tubings and bags have been reported to be released into the solutions contained within these and other plastic containers. For example phthalate esters have been found in whole blood, or plasma stored in plastic bags; and from perfusion studies with rat livers, it appears that at least one phthalate ester (di-2ethylhexyl phthalate-or DEHP) is not metabolized but is rather accumulated by the liver and by human tissues. Furthermore, the latter plasticizer (DEHP) has been shown to be present in bovine, rat, rabbit and dog heart mitochondria, and to be also teratogenic in rats. Studies from our laboratories on the properties, absorption and metabolism of 2-alkylalkanoates, would suggest that the steric hindrance of the 2-ethyl grouping in DEHP would alter absorption rates, and most certainly not be easily hydrolized. Hence, it would be compatible with our studies and reasonable to expect that this, and similar compounds, would not be easily metabolized, but would be deposited in tissues. In the present proposal, using double labeled phthalate esters synthesized in our laboratories, we are hopeful to study their (a) mode of absorption from the G.I. tract, (b) tissue desposition, (c) metabolic fate, and (d) excretion pathways. These studies will be carried out principally in thoracic duct-cannulated rats, and by standard metabolic balance technques.